1. Field of the Invention
The present invention relates to an image heating apparatus that can operate as a heating fixing apparatus (fixing device) installable in an image forming apparatus, such as an electrophotographic copying machine, an electrophotographic printer, or the like.
2. Description of the Related Art
An external heating type fixing apparatus is known as a heating fixing apparatus (fixing device) installable in an electrophotographic copying machine or a printer. The external heating type fixing apparatus includes a heating member (e.g., a heater), a fixing roller heated by the heating member, and a pressing roller contacting the fixing roller to form a nip portion. As discussed in Japanese Patent Application Laid-Open No. 2003-186327, this type of fixing apparatus conveys a recording material carrying an unfixed toner image so that the surface carrying the toner image faces the fixing roller, while the recording material is held at the nip portion and heated by the heating member. Thus, the unfixed toner image on the recording material can be heated and fixed on the recording material.
The external heating type fixing apparatus is roughly classified into a contact-type fixing apparatus that causes the heating member to directly contact an outer circumferential surface of the fixing roller, and a non-contact type fixing apparatus that uses a halogen heater or another non-contact type heating member capable of heating the surface of the fixing roller. When the external heating type fixing apparatus is a contact-type, a heating member (e.g., a ceramic heater) directly contacts the surface of the fixing roller to transfer heat. Therefore, the heat transfer efficiency of the contact-type fixing apparatus is high compared to that of the non-contact type fixing apparatus.
Moreover, the external heating type fixing apparatus of the contact-type is roughly classified into a sliding contact-type fixing apparatus and a movable contact-type fixing apparatus. The sliding contact-type fixing apparatus includes a heating member, which is brought into contact with the surface of a fixing roller and is slidable. The movable contact-type fixing apparatus includes a heating film, which is heated by a heating member and moves together with the surface of a fixing roller, as discussed in Japanese Patent Application Laid-Open No. 2002-236426.
In these fixing apparatuses, when an unfixed toner image on a recording material (e.g., recording paper) is fixed, a small amount of dirt (offset toner, paper dust, etc.) adheres to the outer circumferential surface of a fixing member (e.g., the fixing roller, a fixing film, etc.). If the dirt remains on the surface of the fixing member due to repeated printing, the dirt may be transferred from the fixing member to recording paper and generate a defective image.
Therefore, as discussed in Japanese Patent Application Laid-Open No. 3-65167, a cleaning blade capable of scraping the dirt off the surface of the fixing member can be provided. As discussed in Japanese Patent Application Laid-Open No. 2001-154529, a cleaning weave capable of wiping the dirt off the surface of the fixing member can be provided. The cleaning blade and the cleaning weave can remove the dirt off the surface of the fixing member, and can reduce generation of a defective image.
However, if the above-described conventional fixing apparatus uses the cleaning blade to clean the surface of the fixing member, the cleaning by the cleaning blade may be insufficient and a defective image may be generated. As described above, when the unfixed toner image on a recording paper is fixed, a small amount of dirt (offset toner, paper dust, etc.) adheres to the surface of the fixing member.
The cleaning blade, when it is used to clean the surface of the fixing member, can collect the paper dust or any dirt stable against the heat from the fixing member. However, the toner or another dirt that melts by the heat from the fixing member may pass through the blade. If the fixing apparatus uses a cleaning pad (felt, unwoven fabric, etc.) to clean the surface of the fixing member, the toner melted by the heat from the fixing member may partly pass through the cleaning pad and may be discharged to the surface of the fixing member. The toner discharged on the surface of the fixing member is transferred to a subsequent recording paper conveyed by the fixing nip portion and soils an image on the subsequent recording paper.
On the other hand, when the fixing apparatus uses a cleaning weave to clean the surface of the fixing member, the cleaning weave can periodically change its cleaning surface to prevent the melted toner from passing through the cleaning weave. However, the configuration of the fixing apparatus becomes complicated and the cost of the fixing apparatus increases.